What technique did you use when drilling the hole in the 4" mandrel pipe?
My 1997 Grand Prix GTP progress build thread! Mods At The Moment: 160+ Amps Alternator. Mods I Will Be Doing In 2015: Speed Daddy Headers, 3.4" Modular Pulley System, Open Air Intake, BillBoost Tune, TransGo SKĀ® 4T65E Transmission Shift Kit, 180* Thermostat